NGWS SDK Documentation  

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Compiler Error C3250

'class' : invalid base class for value type 'class'

A value class can only inherit from an interface or from Microsoft.Runtime.Object; any other base class is illegal.

The following sample generates C3250:

valueclass VC1 {
   int i;
};

valueclass VC2 : public VC1 {   // C3250; VC1 not an interface of Object
   int j;
};

If you intend to have VC2 contain an instance of VC1, declare VC1 as a member:

valueclass VC2 {
   VC1 m_vc1;
   int j;
};